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Single-Walled Carbon Nanotubes: A theoretical study of stability, growth and properties
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. (Tillämpad fysik)ORCID iD: 0000-0003-1542-6170
2019 (English)Doctoral thesis, comprehensive summary (Other academic)Alternative title
Enkelväggiga Kolnanorör : En teoretisk studie av stabilitet, tillväxt och egenskaper (Swedish)
Abstract [en]

Since their discovery over 25 years ago, scientists have explored the remarkable properties of single-walled carbon nanotubes (SWCNTs) for use in high-tech materials and devices, such as strong light-weight composites, efficient electrical wires, supercapacitors and high-speed transistors. However, the mass production of such materials and devices is still limited by the capability of producing uniform high-quality SWCNTs. The properties of a SWCNT are determined by the orientation of the hexagonal grid of carbon atoms constituting the tube wall, this is known as the chirality of the SWCNT.

Today's large-scale methods for producing SWCNTs, commonly known as growth, give products with a large spread of different chiralities. A mixture of chiralities give products with a mixture of different properties. This is one of the major obstacles preventing large-scale use of SWCNTs in future materials and devices. The goal is to achieve growth where the resulting product is uniform, meaning that all SWCNTs have the same chirality, a process termed chirality-specific growth. To achieve this requires a deep fundamental understanding of how SWCNTs grow, both from an experimental and a theoretical perspective.

This work focuses on theoretical studies of SWCNTs and their growth mechanisms. With the goal of achieving a deeper understanding of how chirality arises during growth and how to control it. Thus, taking us ever closer to the ultimate goal of achieving chirality-specific growth. In this thesis, an introduction to the field is given and the current research questions are stated. Followed by chapters on carbon nanomaterials, SWCNTs and computational physics. A review of the state-of-the-art experimental and theoretical works relating to chirality specific growth is also given.

The results presented in this thesis are obtained using first principle density functional theory calculations. Results show that the stability of short SWCNT-fragments can be linked to the products observed in experiments. In 84% of the investigate cases, the chirality of experimental products matches the chirality of the most stable SWCNT-fragments (within 0.2 eV). Further studies also reveal a previously unknown link between the stability of SWCNT-fragments and their length. Calculations show that at specific lengths the most stable chirality changes. Thus, introducing the concept of a switching length for SWCNT stabilities.

This newly found property of SWCNTs is used in combination with previously published works to create a state-of-the-art analytical model to investigate growth of SWCNTs any temperature. Results from the model show that the most stable chirality obtained is dependent on the diameter, length of the SWCNT, the growth temperature and the composition of the catalyst. Finally, a detailed study on the ability of catalyst metals to sustain SWCNT growth points to Pt as an interesting candidate to achieve growth of rarely seen chiralities. The new knowledge gained from these results takes us even closer to achieving chirality-specific growth.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2019.
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Condensed Matter Physics Atom and Molecular Physics and Optics
Research subject
Applied Physics
Identifiers
URN: urn:nbn:se:ltu:diva-73708ISBN: 978-91-7790-370-3 (print)ISBN: 978-91-7790-371-0 (electronic)OAI: oai:DiVA.org:ltu-73708DiVA, id: diva2:1305822
Public defence
2019-06-13, E231, Luleå, 09:00 (English)
Opponent
Supervisors
Available from: 2019-04-23 Created: 2019-04-18 Last updated: 2019-06-14Bibliographically approved
List of papers
1. On the Stability and Abundance of Single Walled Carbon Nanotubes
Open this publication in new window or tab >>On the Stability and Abundance of Single Walled Carbon Nanotubes
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2015 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 5, article id 16850Article in journal (Refereed) Published
Abstract [en]

Many nanotechnological applications, using single-walled carbon nanotubes (SWNTs), are only possible with a uniform product. Thus, direct control over the product during chemical vapor deposition (CVD) growth of SWNT is desirable, and much effort has been made towards the ultimate goal of chirality-controlled growth of SWNTs. We have used density functional theory (DFT) to compute the stability of SWNT fragments of all chiralities in the series representing the targeted products for such applications, which we compare to the chiralities of the actual CVD products from all properly analyzed experiments. From this comparison we find that in 84% of the cases the experimental product represents chiralities among the most stable SWNT fragments (within 0.2 eV) from the computations. Our analysis shows that the diameter of the SWNT product is governed by the well-known relation to size of the catalytic nanoparticles, and the specific chirality is normally determined by the product’s relative stability, suggesting thermodynamic control at the early stage of product formation. Based on our findings, we discuss the effect of other experimental parameters on the chirality of the product. Furthermore, we highlight the possibility to produce any tube chirality in the context of recent published work on seeded-controlled growth.

National Category
Other Physics Topics
Research subject
Tillämpad fysik
Identifiers
urn:nbn:se:ltu:diva-8424 (URN)10.1038/srep16850 (DOI)000364945200001 ()26581125 (PubMedID)2-s2.0-84947723240 (Scopus ID)6ef8fdc5-e0fd-40e1-8ac0-14060031f749 (Local ID)6ef8fdc5-e0fd-40e1-8ac0-14060031f749 (Archive number)6ef8fdc5-e0fd-40e1-8ac0-14060031f749 (OAI)
Note
Validerad; 2015; Nivå 2; 20151119 (danhed)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2019-06-14Bibliographically approved

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